1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to the field of geophysical data acquisition and aggregation. In particular, the embodiments disclosed herein relate to a modular autonomous geophysical data recording device and a method and system for collecting data from, and providing power to, such devices.
2. Discussion of the Background
Geophysical data is useful for a variety of applications such as weather and climate forecasting, environmental monitoring, agriculture, mining, and seismology. As the economic benefits of such data have been proven, and additional applications for geophysical data have been discovered and developed, the demand for localized, high-resolution, and cost-effective geophysical data has greatly increased. This trend is expected to continue.
For example, conventional seismic imaging systems typically record narrow azimuth data. However, complex geological formations, such as the salt bodies of the Gulf of Mexico, have resulted in the need of more sophisticated seismic images.
A current solution is the use of all-azimuth illumination and data acquisition. One example of all-azimuth seismic data acquisition uses autonomous seismometer nodes. In a typical application, the nodes are battery-powered with precise clocks for time synchronization. The nodes may remain on the seafloor or on land for an extended period of time for the recording of acoustic waves coming from a source and energy that is reflected from subsurface formations.
Autonomous seismometer nodes such as those described in U.S. Pat. No. 7,646,670, which is incorporated herein by reference, are essentially self-contained recording stations comprising sensors, a recording unit, a reference clock, and a power source. Seismometer nodes may be deployed in areas where streamers or cabled systems are impractical. Some are intended for long term autonomous acquisition for up to 6 months. Data are typically accessed after recovery of the units.
Seismometer nodes can be used for passive seismic monitoring or for recording seismic energy generated by acoustic sources. The latter method can be used for oil and gas exploration, or for production monitoring. The seismometer nodes may be retrieved, at which time, the data are downloaded and batteries may be replaced or recharged for the next deployment. However, replacing or recharging the seismometers in the field and extracting the data therefrom slow down the costly retrieval process, particularly for ocean bottom surveys.
Similar to seismometers, other geophysical sensing units are often placed in locations that are remote and difficult to reach, such as mountainous regions, glacial regions, jungles, forests, underground mines, downhole locations, and underwater. Direct radio or satellite communications to such locations may not be possible or cost effective. Installing and maintaining data collection cables is also costly and may be impractical in some environments. Consequently, many deployed geophysical sensing units are autonomous units that are powered by batteries and require retrieving or exchanging the sensing unit, in order to recharge the batteries and extract the geophysical data record therein.
The need to retrieve or exchange geophysical sensing units typically requires acquiring a large number of redundant geophysical sensing units—which can be quite costly. Furthermore, each newly deployed geophysical sensing unit may need to be set up with various parameters by a technician (e.g. the precise geophysical location, elevation, or depth of the device), and tested at the deployed location, in order to ensure that the required geophysical data is properly acquired and recorded by the device.
Given the foregoing, a different approach is warranted. Specifically, methods and means are needed to provide power to and extract data from geophysical sensing units without removing those units from their deployed locations.